1. Field of the Invention
The invention relates to a wheel module and particularly to a wheel module applied to a wheelchair.
2. Description of Related Art
Nowadays, because of age and injuries, many handicapped people use wheelchairs as a mobility device. In home environments, many times space is limited so it is difficult for a wheelchair to enter and exit, causing inconvenience in mobility.
In order to improve the mobility in narrow spaces, wheelchairs have adopted a method of driving with a motor for the left and right wheels. Even though this method allows the wheelchair to rotate in place, the wheelchair can not move sideways. For example, if a kitchen counter and a oven top are located on the same side in a kitchen, when the wheelchair user wants to move from the kitchen counter to the oven top, he or she must first move back, turn, move towards the oven top, and then turn to face the oven top. The movement is very inconvenient, and so sideways movement in a wheelchair is very important for a user.
FIG. 9 shows a bottom view of a conventional wheelchair. The four wheel modules 500 of the wheelchair 20 are all used with omni-wheel, and each wheel module 500 is driven by an independent motor 600. In addition, since a roller 510 and a wheel shaft 520 around the wheel frame of the wheelchair 20 form a 45 degree angle, not only can the wheelchair 20 rotate in place, but it can also move in parallel from left to right. Even though the design improves the mobility of wheelchairs in narrow spaces, however, the design relies on a wheel shaft 520 and a roller 510 for rotation, respectively generating two different velocity vector components with different directions. Thus, the two different velocity directions mutually offset to control movement direction, thus causing a portion of power outputted by the motor 600 being neutralized. This causes slow movement velocity and consumes unnecessary electric power.